In a communication network, a router needs to be maintained periodically. As used herein, the term “router” refers to any suitable device that can route, forward or switch traffic in the communication network based on route selection. Some examples of the router include, but are not limited to, a switch, a gateway, a server and the like. The term “maintenance” refers to any types of maintenance, including, but not limited to, software upgrade, software update, hardware replacement and the like.
Conventionally, while a router is being maintained, the path passing through the router is replaced by a backup path, which may be determined in advance, and thereby bypassed. An example of such a route switch is the technology of fast reroute (FRR). According to the FRR, when the router detects that its next hop router goes down, for example, due to maintenance, the router can switch traffic to a predetermined backup path. The procedure of the FRR inevitably introduces a traffic interruption and therefore causes a traffic loss.
The technology of In-Service Software Upgrade (ISSU) was proposed to avoid the traffic loss during maintenance. According to the ISSU, a router is provided with redundant control and line cards. The redundant control cards include a primary control card and a backup control card, and the redundant line cards include a primary line card and a backup line card. If the control cards need to be upgraded, the backup control card is first upgraded while the primary control card keeps active. Upon the completion of the upgrading of the backup control card, the backup control card is switched to be active, and the primary control card is upgraded. The procedure of upgrading the line cards is similar to the procedure of the control cards as described above. With the ISSU, there is no traffic interruption during the maintenance of the router. However, the ISSU is only applicable to software maintenance. In addition, the redundancy of the cards, in particular, the redundancy of the line cards, is not widely used due to a high cost.
Therefore, there is a need for more efficient and cost-effective solution of router maintenance.